1. Field of the Invention
The present invention related to communication, and provides methods for allocating transmission power over channels.
2. Description of Related Art
A problem often encountered in communication, either wireline or wireless, is that of allocating power over a set of parallel non-interacting channels sharing a common transmitter.
Although diverse criteria can be used in order to decide which fraction of the available power is allocated to each of the channels, a particularly enticing one is the maximization of the sum mutual information, which specifies the largest data rate per unit bandwidth that can be conveyed with arbitrary reliability. In the case that the noise impairing the communication is Gaussian, the mutual information is maximized if the transmitted signals are also Gaussian and the power is allocated over the available orthogonal channels according to the well-known waterfill policy.
Despite their optimality, however, Gaussian signals can never be realized in practice because of their infinite and continuous support. Rather, in actual communication systems the signals are modulated using discrete constellations. No solution is known for the power allocation over parallel channels that maximizes the mutual information when the transmitted signals are not Gaussian, and the waterfill policy is often invoked for non-Gaussian signals even though it is no longer optimal in that case.